SU101115A1 - Calcium fluoride production method - Google Patents

Description

The existing method for producing calcium fluoride is the flotation of fluorspar. Calcium fluoride, produced by the flotation of fluorspar, is scarce due to the increased demand for natural fluorine compounds for various industries.

The proposed method makes it possible to produce calcium fluoride with a content of 98-99% Сар2 from products of superphosphate production based on fluorosilicic acid or fluorine-containing II gases.

The essence of the method consists in obtaining ammonium fluoride or alkaline fluoride (NaF or KF) from an aqueous solution of hydrofluoric acid or gases containing Sip.} And a working solution of ammonia (or a working solution of caustic alkali or carbonate alkali):

3 51p4 + 12 NH4OH 12 NH, P + H-3C3Hg + bNZO;

or 3SiP4 + 12NaOH 12NaP + + ЗЗУз + 6Н2р

and in the further reaction of a solution of ammonium fluoride or alkaline fluoride with lime milk, for example.

GNH-iP -f ЗСа (ОН) .. ЗСаР., -Г + 6NH4OH, 6NaP + ЗСа (ОН)., ЗСаР., +

-GNaOH,

with limestone:

6NH., P + ZSaCO, ZSaR, -3 (MN.,) 2Coz,

or 6NaP + ЗСаСОз ЗСаР. + + 2Na2CO3.

Example 1. An aqueous solution of hydrofluoric acid, obtained, for example, by absorbing fluorine-containing gases from superphosphate chambers or dust-free gases from evaporation of phosphoric acid with a concentration of HoSiPs 6-20% and higher, freed from silica gel, is exposed to a working solution of ammonia, taken in a small excess . The resulting solution is separated from SiOj by filtration or centrifugation at a temperature not higher than 40 °, and the SiO-j precipitate is washed with water having a temperature below 40. Wash water is used either for the subsequent preparation of milk of lime or for the absorption of fluorine-containing gases. While stirring at a temperature not exceeding 40 ° C, milk powder, freed from insoluble SiO impurities and silicates, is added to the filtrate, or

calcium carbonate. The ratio of reagents is stoichiometric or with an insignificant (1-5%) excess of ammonium fluoride. The reaction time is 2-5 hours. Calcium fluoride is separated from the aqueous ammonia solution by filtration or centrifugation. An aqueous ammonia solution is recycled to absorb fluorine-containing gases, and the calcium fluoride precipitate is washed and dried.

PRI mme R 2. In the case of replacement of the working solution of ammonia with a working solution of caustic alkali (KOH or NaOH) or carbonate oil; elites (KA2CO3 or K2CO3), the conditions of both reactions of the process described in example 1 (neutralization of SiF.t or K2SiF6 and caustification the resulting fluoride) remains largely unchanged, with the exception of the temperature, which can be significantly increased due to the significantly lower volatility of NaF and KF compared to NH4F, in particular, during the reaction of causticidia up to 80-100 °.

Subject invention

Claims (2)

1. A method for producing calcium fluoride from fluorine-containing gases of superphosphate factories or hydrofluoric acid is characterized in that, in order to obtain a clean, easily filtered and free of colloidal silicic calcium fluoride, gases containing fluorine or hydrofluoric hydrofluoric acid are treated with an liquor or an liquor, and an liquor is used in a set of liquids that come up with an amount of an omi-liqueur. then the obtained alkaline fluoride, after the separation of silicic acid, is brought into contact with lime or lime milk, or calcium carbonate . 2. A method according to claim 1, characterized in that, in order to eliminate the consumption of scarce alkalis, a circulating alkali solution obtained by treating alkaline fluoride after filtering calcium fluoride is used to treat fluorine-containing gases or hydrofluoric acid.